Although such a viewpoint may seem controversial, the concept of the particle is rather tenuous even in the standard view of QFT. C. Rovelli and D. Colosi [1]}, for instance, correctly note that localized particle detectors do not measure Fock states, which are eigenstates of the global operators \(\hat{N}\)  and \(\hat{H}\) , but instead measure the eigenstates of local operators. Moreover, investigations of QFT in curved space-time in the 1970's [2]}[3]}[4]} give strong hints that the particle concept itself is highly problematic to begin with, leading some physicists, such as Davies [5]}, to claim that “particles do not exist."
